Russell Watson faces months of debilitating radiotherapy to shrink the remains of a large tumour which brain surgery left behind, doctors revealed last night.

The 40-year-old opera star, who was rushed into hospital for the emergency operation last week, will start the treatment in six weeks' time.

His manager Richard Thompson said last night: "There is a residual tumour that they have to kill off. It sounds a bit alarming. The only way of dealing with it now is through radiotherapy.

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"He will have to wait six weeks from his discharge to start the treatment. We know the radiotherapy will take it out of him."

Watson's manager also spoke of fears that the surgery - during which doctors had to go into his brain through the roof of his mouth - may affect his award-winning voice in the long-term.

Mr Thompson said: "There was some concern because when he came out of theatre he was having trouble speaking, but he's speaking normally now.

"It is a worry, but we don't know how much of a worry.

"When he had the operation a year ago we didn't want to go through the mouth for obvious reasons, but there was no option this time. He's got stitches in his mouth and they'll need to heal. But he will be singing again."

Watson - who is known as The Voice and boasts a massive five million record sales - underwent a three-hour operation on the tumour at the private Alexandra Hospital in Cheadle, Cheshire, on Thursday.

The father of two was first struck down with a brain tumour 'the size of a cricket ball' last year.

He appeared to make a full recovery from an operation, but it emerged the tumour had regrown when he fell ill in a recording studio last week.

The first operation was carried out by going through his nose, but scar tissue prevented doctors from being able to do the same this time.

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Mr Thompson also said the support for the singer had been 'off the scale'.

Friends and family - including daughters Hannah, eight, and Rebecca, 12 - visited him over the weekend before he was taken out of intensive care on Monday.

Michael Stroud, executive director of The Alexandra Hospital, said: "Russell Watson is progressing well. He has been moved out of our Intensive Care Suite, but is still under constant supervision.

"It is too early to say when he will be discharged or what the recovery period will involve. For now he will continue to be monitored very closely."

Meanwhile, the singer's dad Tim, 61, a maintenance man, from Leigh, Greater Manchester, visited again with Russell's grandmother Phyllis Aldred, 86, and he said: "She always loves seeing him - she is one of his biggest fans.

"He calls her Crnab (Crnab) - a name she got form our days playing Scrabble - we'll have to do that again one day soon with Hannah and Rebecca - but the girls will probably beat both of us. I only hope the brain surgeon hasn't turned him into a Scrabble genius."